This invention relates to a semiconductor device using a fluorine-containing carbon film as an inter-layer dielectric film, and a manufacturing method thereof.
Various efforts, such as miniaturization of patterns and employments of multi-layered structure of circuits are being made toward progressively high integration of semiconductor devices. There is a technique for making wirings in the form of a multi-layered structure as one of those efforts. In order to employ a multi-layered wiring structure, an n-th wiring layer and an (n+1)-th wiring layer are connected by a conductive layer, and a thin film called an inter-layer dielectric film is formed in the area excluding the area of the conductive layer.
SiO2 film is a representative inter-layer dielectric film. Recently, however, it has been desired to lower relative dielectric constants of inter-layer dielectric films for the purpose of further increasing operation speeds of devices, and researches are being made about materials of inter-layer insulating films. That is, the relative dielectric constant of a SiO2 film is about 4, and efforts are being made to find out materials having lower relative dielectric constants. Among them, a SiOF film whose relative dielectric constant is 3.5 is under progress toward realization, but the inventor is remarking boron nitride (BN) films containing boron (B) and nitrogen (N) and fluorine-containing carbon (CF) films which are lower in relative dielectric constant.
It has been confirmed that BN films have a high adhesiveness and are suitable for use as inter-layer insulating films in that respect, but they exhibit a high hygroscopicity and are thereby changed in relative dielectric constant Some trials including addition of silicon (Si) were made for improvement in that point. However, although addition of Si certainly decreases the hygroscopicity, it undesirably increases the relative dielectric constant. Therefore, BN films are difficult to realize for practical use, and the target has been directed to realization of semiconductor devices using CF films as their inter-layer insulating films.
Manufacturing processes of semiconductor devices, in general, include a process of etching an inter-layer dielectric film for the purpose of making a wiring layer by burying a metal therein. Since both a resist and a CF film are organic films that are approximately equal in etching rate (selectivity), the resist is also etched undesirably when the CF film is etched. To deal with this problem, a film of a material different in etching rate from the CF film is formed between the resist and the CF film as a hard mask before the etching is executed.
Used as the hard mask is a silicon carbide (SiC) film or a silicon nitride (SiN) film. A reason for the use of these films lies in that, although CF films are liable to lose fluorine (F) when heated, SiC and SiN are similar to ceramics, and have a high weather-resistance to fluorine.
However, when a SiC film, for example, is used as the hard mask, a semiconductor device having a multi-layered wiring structure made by stacking CF films results in having a considerably high relative dielectric constant as a whole, since SiC films and SiN films have relative dielectric constants as large as approximately 8. This invites the problems: an increase of the inter-wiring capacitance in the entire semiconductor device; a signal delay upon sending a digital signal; and a slow-down of the transmission rate of the signal.
The invention has been made under these circumstances, and its object lies in decreasing the total inter-wiring capacitance in a semiconductor device using a fluorine-containing carbon film, or the like, as its inter-layer insulating film.
For accomplishing the above-indicated object, according to the invention, there is provided a semiconductor device having a multi-layered wiring structure, comprising a plurality of wiring layers made of a metal, a dielectric layer provided between every adjacent two of said wiring layers, and a compound layer which is composed of a compound containing boron and nitrogen and is located at least on one side of said dielectric layer.
Additionally, according to the invention, there is provided a manufacturing method of a semiconductor device having a multi-layered wiring structure, comprising the steps of forming a dielectric layer, forming a compound layer composed of a compound containing boron and nitrogen, on said dielectric layer, forming a predetermined pattern on said compound layer using a resist composed of an organic material, and etching said dielectric layer to shape it into a predetermined pattern using an etching gas capable of etching both said dielectric layer and said resist.